1. Field of the Invention
This invention relates to an elevator control apparatus which is capable of estimating with a high degree of accuracy whether or not an elevator car will be delayed (the delay of the elvator car) in reaching each floor of a building and the amount of the delay.
2. Description of the Related Art
In a conventional elevator systems having a plurality of elevator cars, group control operation is generally conducted. An example of such a group control operation is the allocation method that matches elevator cars with calls. The allocation method is designed to improve the operation efficiency of and shorten the waiting time for a car by determining an evaluated value for each car immediately after a hall call is registered, by selecting the car which has the best evaluated value as the car to be allocated, and by making only that car respond to the hall call.
In the recent group controlled elevator apparatus, arrival of the allocated car is in general notified to the passengers who are waiting for the car by lighting the forecasting lamp of the allocated car before the car reaches the floor. This is called "forecasting". When this forecasting is made, the passengers who are waiting for the elevator car are given notice of the elevator car to be put into service first, and thus can wait for the arrival of the car in front of it.
However, an elevator car which has not been forecast may arrive faster than the forecast car in response to the car call (this is called "wrong forecasting"). Since such wrong forecastings confuse the passengers who are waiting at the hall, they are undesirable.
Various methods for preventing wrong forecasting have been proposed. For example, Japanese Patent Publication No. 47787/1987 discloses an elevator group-control apparatus which is designed to select, as a car to be allocated, a car which has the minimum general evaluated value when a hall call is registered. The general evaluated value is the sum of an evaluated waiting time value and an evaluated wrong forecasting value. The evaluated waiting time value is the sum of the squares of the estimated waiting times of all the hall calls when the hall call is virtually allocated to the individual elevator cars. The evaluated wrong forecasting value is obtained by weighting the sum of the wrong forecasting probabilities (an index indicating the possibility that the car which is not forecast arrives first) for all the hall calls when the hall call is virtually allocated to the individual cars.
In the above-described group control system, the wrong forecasting probability is obtained by the following equation:
Wrong forecasting probability=first arrival probability x car call generation probability
The first arrival probability is an index which takes variations in the estimated arrival time of the car into consideration and which indicates the possibility that an elevator car other than the forecast (allocated) car will reach the hall where forecasting is made first (regardless of the stoppage of that car at that hall). The first arrival probability is calculated on the basis of overlapping of the probability distribution of the arrival times of the forecast and non-forecast elevator cars and the difference in the estimated arrival time (the first arrival time difference) between the forecast car and the non-forecast car. The car call generation probability is an index which indicates the possibility that the non-forecast car will have a car call on the hall where forecasting is made. When the non-forecast car already has a car call on the floor where forecasting is made, "1.0" is set as the car call generation probability. In other cases, the car call generation probability is set on the basis of the results of statistics conducted on the number of people who get on and off the car with the passengers who get on the car at the floors located between the current floor and the desired floor taken into consideration.
Japanese Patent Laid-Open No. 125580/1983 discloses an elevator group control method in which a difference in the estimated arrival time (car call first arrival time) between the allocated car and the non-allocated car which arrives in response to the car call is weighted by the car call first arrival time and the obtained value is used as one element of the evaluated hall call value.
Japanese Patent Laid-Open No. 36865/1983 discloses an elevator group control method in which the car call first arrival time is weighted by the distance (the number of floors) through which the car which generates car call first arrival must travel until it reaches the floor which generates the car call first arrival and the obtained value is used as one element of the evaluated hall call value.
Thus, allocation of the elevator car to the hall call is made on the basis of the estimated value of the car delay that is, the estimated car delay (which may be the wrong forecasting probability, the first arrival probability, the first arrival time difference, the car call first arrival time, or a value obtained by conducting a predetermined weighting on the car call first arrival time). Consequently, the waiting time for the hall call can be shortened and generation of wrong forecasting can be reduced.
Other elevator group control methods which have been proposed include one (Japanese Patent Publication No. 56708/1983) in which a car having the minimum wrong forecasting probability for a newly registered hall call is allocated to the hall call, one (Japanese Patent Publication No. 56708/1983) in which, when the wrong forecasting probability for a newly registered hall call exceeds a predetermined value, allocation is delayed until that probability becomes less than the predetermined value, and one (Japanese Patent Publication No. 46151/1987) in which a car having the minumum total sum of the wrong forecasting probabilities for the new hall call and already allocated hall calls is allocated to a hall call.
In the above-described conventional methods, an inaccurate estimated car delay makes the obtained evaluated value insignificant as the reference value with which a car to be allocated is selected, and thus increases generation of wrong forecasting. Thus, accuracy of the estimated car delay greatly affects the performance of the group control system.
Group control methods intended to prevent wrong forecasting by means other than the control of the hall call allocation have also been proposed. Such methods include one (Japanese Patent Laid-Open No. 12577/1988) in which, when a non-forecast car estimated to arrive faster than the forecast car is detected, an arrival accelerating instruction is output to the forecast car so as to decrease the time required for that car to stop and pass the floors before it arrives at the floor where forecasting is made; one (Japanese Patent Laid-Open No. 8180/1988) in which an arrival postponing instruction is output to the non-forecast car so as to increase the time required for that car to stop and pass the floors before it arrives at the floor where forecasting is made; and one (Japanese Patent Laid-Open No. 2850/1978) in which lighting of the forecasting lamp is postponed until the wrong forecasting probability fulfills a predetermined condition.
Other group control methods which use the estimated car delay in order to achieve the objects other than prevention of wrong forecasting have also been proposed. Such group control methods include one (Japanese Patent Laid-Open No. 153551/1977) in which, when there is the possibility that wrong forecasting occurs, the first arrival car is identified so as to prevent passenger confusion; and one (Japanese Patent Laid-Open No. 29057/1977) in which, when the car which is expected to arrive first at the floor comes within a predetermined distance from the floor, allocation and forecasting are changed to that car which arrives first. In these group control systems, accuracy of the estimated car delay greatly affects the performance of the group control operation.
To obtain an accurate car delay, the estimated arrival time, the car call generation probability, or the probability distribution of arrival time must be calculated with a high degree of accuracy. Conventionally, the estimated arrival time is basically calculated first by calculating the time required for the car to travel from the current position to the objective floor on the basis of the distance between the current position and the objective floor, then by calculating the time (stoppage time) during which the car stops at the floors before the car reaches the objective floor on the basis of the number of times the car stops, and finally by adding these two types of times, as is described in Japanese Patent Publication No. 20742/1979. To improve the accuracy with which the arrival time is estimated, the estimated value of the stoppage time is corrected in accordance with the state of the car at the current car positioned floor (Japanese Patent Publication No. 40074/1982), the estimated value of the stoppage time is corrected in accordance with the number of people who get on or off the car or the type of responding call (Japanese Patent Publication No. 40072/1982), the estimated value of the stoppage time is corrected on the basis of the estimation of the car call generation (Japanese Patent Publication No. 34111/1988), or the estimated value of the running time is corrected with the change in the running direction of the car on its way to the objective floor taken into consideration (Japanese Patent Publication No. 16293/1979).
Japanese Patent Laid-Open No. 275381/1989 discloses a group-control apparatus which selects the car to be allocated to the hall call on the basis of the results of the operation conducted using the neural net corresponding to the neurons of the human's brain. However, no consideration is given to the improvement of the accuracy with which the estimated car delay is operated.
In the conventional elevator control apparatus, various elements, including the state of the floor where the car is to stop, the state of the car, the type of responding call, the estimated number of passengers who get on or get off at the floors where the car is to stop, estimation of generation of car call, estimation of allocation of the car to a new hall call, estimation of the floor where the car changes the running direction, and the current traffic on each floor, are each used as one element of calculation in order to operate the estimated car delay with a high degree of accuracy, as stated above.
However, when all of these elements are contained in the calculation which is performed to obtain estimation with ever-changing complicated traffic taken into consideration, the operation expression of an accurate estimated car delay becomes more complicated. Now that there is a limitation to the human ability, it is difficult to develop new procedures for determining estimated car delay which ensure improved operation accuracy. Furthermore, detailed operation for the estimation increases the time required for the operation and, hence, makes quick allocation of the car and forecasting of the allocated car impossible.